Fog controls biological cycling of soil phosphorus in the Coastal Cordillera of the Atacama Desert.

Soils in hyper-arid climates, such as the Chilean Atacama Desert, show indications of past and present forms of life despite extreme water limitations. We hypothesize that fog plays a key role in sustaining life. In particular, we assume that fog water is incorporated into soil nutrient cycles, with the inland limit of fog penetration corresponding to the threshold for biological cycling of soil phosphorus (P).

Does metabolic water control the phosphate oxygen isotopes of microbial cells?

The oxygen isotopes ratio (δO) of microbial cell water strongly controls the δO of cell phosphate and of other oxygen-carrying moieties. Recently it was suggested that the isotopic ratio in cell water is controlled by metabolic water, which is the water produced by cellular respiration. This potentially has important implications for paleoclimate reconstruction, and for measuring microbial carbon use efficiency with the O-water method.

Understanding soil selenium accumulation and bioavailability through size resolved and elemental characterization of soil extracts.

Dietary deficiency of selenium is a global health threat related to low selenium concentrations in crops. Despite the chemical similarity of selenium to the two more abundantly studied elements sulfur and arsenic, the understanding of its accumulation in soils and availability for plants is limited. The lack of understanding of soil selenium cycling is largely due to the unavailability of methods to characterize selenium species in soils, especially the organic ones.

Analysis of oxygen isotopes of inorganic phosphate (δO) in freshwater: A detailed method description for obtaining oxygen isotopes of inorganic phosphate in environmental water samples.

The ability to identify the origin of phosphorus and understand processes controlling P cycling is essential for designing effective mitigation and restoration of eutrophic freshwater ecosystems. The oxygen isotope composition of orthophosphate (δO) has significant potential as a tracer for P entering freshwater ecosystems. However, methods of analysis of δO are still in their preliminary stages and have proven challenging to implement for new practitioners.

New Ag PO comparison material for stable oxygen isotope analysis.

Rationale: A silver phosphate reference material (Ag PO ) for the measurement of stable oxygen isotope compositions is much needed; however, it is not available from the authorities distributing reference materials. This study aims to fill this gap by calibrating a new Ag PO stable isotope comparison material produced by the University of Natural Resources and Life Sciences (BOKU).

Methods: Aliquots of Ag PO were distributed to four laboratories who frequently measure the δ O value in Ag PO ; the University of Natural Resources and Life Sciences (BOKU), the University of Western Australia (UWA), the University of Helsinki (UH), and the Helmholtz Centre for Environmental Research (UFZ).

Tracing uptake and translocation of phosphorus in wheat using oxygen isotopes and mathematical modelling.

Understanding P uptake in soil-plant systems requires suitable P tracers. The stable oxygen isotope ratio in phosphate (expressed as δ O ) is an alternative to radioactive labelling, but the degree to which plants preserve the δ O value of the P source is unclear. We hypothesised that the source signal will be preserved in roots rather than shoots.

Changes of oxygen isotope values of soil P pools associated with changes in soil pH.

Field data about the effect of soil pH on phosphorus (P) cycling is limited. A promising tool to study P cycling under field conditions is the O:O ratio of phosphate (δO). In this study we investigate whether the δO can be used to elucidate the effect of soil pH on P cycling in grasslands.

Combining spectroscopic and isotopic techniques gives a dynamic view of phosphorus cycling in soil.

Current understanding of phosphorus (P) cycling in soils can be enhanced by integrating previously discrete findings concerning P speciation, exchange kinetics, and the underlying biological and geochemical processes. Here, we combine sequential extraction with P K-edge X-ray absorption spectroscopy and isotopic methods (P and O in phosphate) to characterize P cycling on a climatic gradient in Hawaii. We link P pools to P species and estimate the turnover times for commonly considered P pools.

A dual isotopic approach using radioactive phosphorus and the isotopic composition of oxygen associated to phosphorus to understand plant reaction to a change in P nutrition.

Background: Changing the phosphorus (P) nutrition leads to changes in plant metabolism. The aim of this study was to investigate how these changes are reflected in the distribution of P and the isotopic composition of oxygen associated to P (δO) in different plant parts of soybean ( cv. Toliman).

Tracing the sources and cycling of phosphorus in river sediments using oxygen isotopes: Methodological adaptations and first results from a case study in France.

An essential aspect of eutrophication studies is to trace the ultimate origin of phosphate ions (P-PO) associated with the solid phase of river sediments, as certain processes can make these ions available for algae. However, this is not a straightforward task because of the diversity of allochthonous and autochthonous sources that can supply P-PO to river sediments as well as the existence of in-stream processes that can change the speciation of these inputs and obscure the original sources. Here, we present the results of a study designed to explore the potentials, limitations and conditions for the use of the oxygen isotope composition of phosphate (δOp) extracted from river sediments for this type of tracing.

Phosphate stable oxygen isotope variability within a temperate agricultural soil.

In this study, we conduct a spatial analysis of soil total phosphorus (TP), acid extractable phosphate (PO) and the stable oxygen (O) isotope ratio within the PO molecule (δO ) from an intensively managed agricultural grassland site. Total P in the soil was found to range from 736 to 1952 mg P kg, of which between 12 and 48% was extractable using a 1 M HCl (HCl ) solution with the two variables exhibiting a strong positive correlation. The δO of the extracted PO ranged from 17.

Plant uptake of phosphorus and nitrogen recycled from synthetic source-separated urine.

Urine contains about 50 % of the phosphorus (P) and about 90 % of the nitrogen (N) excreted by humans and is therefore an interesting substrate for nutrient recovery. Source-separated urine can be used to precipitate struvite or, through a newly developed technology, nitrified urine fertilizer (NUF). In this study, we prepared (33)P radioisotope- and stable (15)N isotope-labeled synthetic NUF (SNUF) and struvite using synthetic urine and determined P and N uptake by greenhouse-grown ryegrass (Lolium multiflorum var.

18O enrichment in phosphorus pools extracted from soybean leaves.

The objective of this study was to investigate the isotopic composition of oxygen bound to phosphate (δ(18)O-PO(4)) in different phosphorus (P) pools in plant leaves. As a model plant we used soybean (Glycine max cv Toliman) grown in the presence of ample P in hydroponic cultures. The leaf blades were extracted with 0.

Oxygen isotopes unravel the role of microorganisms in phosphate cycling in soils.

Phosphorus (P) is considered the ultimate limiting nutrient for plants in most natural systems and changes in the distribution of inorganic and organic P forms during soil development have been well documented. In particular, microbial activity has been shown to be an important control on P cycling but its contribution in building up the pool of plant-available P during soil development is still poorly quantified. To determine the importance of different biological processes on P cycling, we analyzed the isotopic composition of oxygen in phosphate (δ(18)O-Pi) from the parent material, soil microorganisms, the available P pool, and from the vegetation along a 150-year soil chronosequence of a glacier forefield.

A method for analyzing the δ18O of resin-extractable soil inorganic phosphate.

Improved tools for tracing phosphate transformations in soils are much needed, and can lead to a better understanding of the terrestrial phosphorus cycle. The oxygen stable isotopes in soil phosphate are still not exploited in this regard. Here we present a method for measuring the oxygen stable isotopes in a fraction of the soil phosphate which is rapidly available to plants, the resin-extractable P.

Culture of cryopreserved ovarian tissue: state of the art in 2008.

This paper reviews the most relevant literature from the past 10 years on different techniques for the culture of fresh and cryopreserved ovarian tissue from animals and humans. Information on strategies for culturing whole ovarian tissue and isolated follicles are provided as well as an updated and comprehensive view of the role that growth factors have in mediating and regulating in vitro folliculogenesis.

Healthy early preantral follicle can be obtained in a culture of frozen-thawed human ovarian tissue of 32 weeks.

The objective of this study was to report morphological and functional evidence of a well-preserved preantral follicle recovered from human frozen-thawed ovarian tissue in a long-term culture. The tissue was originally obtained from a 26-year-old woman with breast cancer. The ovarian cortex was collected by laparoscopy and frozen/thawed and cultured for 32 weeks in minimum essential medium alpha-MEM, supplemented with insulin transferrine selenite (ITS), human serum (HS), antibiotics, follicle-stimulating hormone (FSH).